Substituent Effects on the [N−I−N]+ Halogen Bond
Carlsson, Anna-Carin C.; Mehmeti, Krenare; Uhrbom, Martin; Karim, Alavi; Bedin, Michele; Puttreddy, Rakesh; Kleinmaier, Roland; Neverov, Alexei A.; Nekoueishahraki, Bijan; Gräfenstein, Jürgen et al. (2016). Substituent Effects on the [N−I−N]+ Halogen Bond. Journal of the American Chemical Society, 138 (31), 9853-9863. DOI: 10.1021/jacs.6b03842
Published inJournal of the American Chemical Society
© the Authors, 2016. This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
We have investigated the influence of electron density on the three-center [N–I–N]+ halogen bond. A series of [bis(pyridine)iodine]+ and [1,2-bis((pyridine-2-ylethynyl)benzene)iodine]+ BF4– complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by 15N NMR and by computation of the natural atomic population and the π electron population of the nitrogen atoms. Formation of the [N–I–N]+ halogen bond resulted in >100 ppm 15N NMR coordination shifts. Substituent effects on the 15N NMR chemical shift are governed by the π population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N–I–N]+ halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine]+ complexes. An increased electron density of the halogen bond acceptor stabilizes the [N···I···N]+ bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N–I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N–X–N]+ halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen]+-type synthetic reagents. ...
PublisherAmerican Chemical Society
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Related funder(s)Academy of Finland
Funding program(s)Research post as Academy Professor, AoF
Additional information about fundingThe research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant Agreement No. 259638. We thank the Swedish Research Council (ME 2007:4407; 621-2008-3562) and the Academy of Finland (KR: 263256 and 265328) for financial support, and Professor Stan Brown (Department of Chemistry, Queen’s University) for giving us access to equipment for the UV–vis kinetic experiments. ...
Except where otherwise noted, this item's license is described as © the Authors, 2016. This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.